[flang][debug] Fix issues with local variables. (#98661)

This PR fixes 2 similar issues.
1. As reported in #97476, flang generated executable has inconsistent
behavior regarding values of the local array variables.
2. Variable with save attribute would not show up in debugger.

The reason behind is same for both cases. If a local variable has
storage which extends beyond function lifetime, the way to represent it
in the debug info is through a global variable whose scope is limited to
the function. This is what is used for static local variable in C.
Previously local array worked in cases they were on stack. But will not
show up if they had a global storage.

To fix this, if we can get a corresponding `GlobalOp` for a variable
while processing `DeclareOp`, we treat it the variable as global with
scope set appropriately. A new FIR test is added. A previous Integration
test has been adjusted as to not expect local variables for local
arrays.

With this fix in place, all the issues described in #97476 go away. It
also fixes a lot of fails in GDB's fortran testsuite.

Fixes #97476.

Author: abidh

flang/lib/Optimizer/Transforms/AddDebugInfo.cpp

@@ -49,7 +49,8 @@ class AddDebugInfoPass : public fir::impl::AddDebugInfoBase<AddDebugInfoPass> {
   void handleDeclareOp(fir::cg::XDeclareOp declOp,
                        mlir::LLVM::DIFileAttr fileAttr,
                        mlir::LLVM::DIScopeAttr scopeAttr,
-                       fir::DebugTypeGenerator &typeGen);
+                       fir::DebugTypeGenerator &typeGen,
+                       mlir::SymbolTable *symbolTable);
 
 public:
   AddDebugInfoPass(fir::AddDebugInfoOptions options) : Base(options) {}
@@ -63,7 +64,8 @@ class AddDebugInfoPass : public fir::impl::AddDebugInfoBase<AddDebugInfoPass> {
       mlir::LLVM::DIScopeAttr scope, unsigned line, bool decl);
 
   void handleGlobalOp(fir::GlobalOp glocalOp, mlir::LLVM::DIFileAttr fileAttr,
-                      mlir::LLVM::DIScopeAttr scope);
+                      mlir::LLVM::DIScopeAttr scope,
+                      mlir::SymbolTable *symbolTable);
 };
 
 static uint32_t getLineFromLoc(mlir::Location loc) {
@@ -73,19 +75,32 @@ static uint32_t getLineFromLoc(mlir::Location loc) {
   return line;
 }
 
+bool debugInfoIsAlreadySet(mlir::Location loc) {
+  if (mlir::isa<mlir::FusedLoc>(loc))
+    return true;
+  return false;
+}
+
 } // namespace
 
 void AddDebugInfoPass::handleDeclareOp(fir::cg::XDeclareOp declOp,
                                        mlir::LLVM::DIFileAttr fileAttr,
                                        mlir::LLVM::DIScopeAttr scopeAttr,
-                                       fir::DebugTypeGenerator &typeGen) {
+                                       fir::DebugTypeGenerator &typeGen,
+                                       mlir::SymbolTable *symbolTable) {
   mlir::MLIRContext *context = &getContext();
   mlir::OpBuilder builder(context);
   auto result = fir::NameUniquer::deconstruct(declOp.getUniqName());
 
   if (result.first != fir::NameUniquer::NameKind::VARIABLE)
     return;
 
+  // If this DeclareOp actually represents a global then treat it as such.
+  if (auto global = symbolTable->lookup<fir::GlobalOp>(declOp.getUniqName())) {
+    handleGlobalOp(global, fileAttr, scopeAttr, symbolTable);
+    return;
+  }
+
   // Only accept local variables.
   if (result.second.procs.empty())
     return;
@@ -138,7 +153,10 @@ mlir::LLVM::DIModuleAttr AddDebugInfoPass::getOrCreateModuleAttr(
 
 void AddDebugInfoPass::handleGlobalOp(fir::GlobalOp globalOp,
                                       mlir::LLVM::DIFileAttr fileAttr,
-                                      mlir::LLVM::DIScopeAttr scope) {
+                                      mlir::LLVM::DIScopeAttr scope,
+                                      mlir::SymbolTable *symbolTable) {
+  if (debugInfoIsAlreadySet(globalOp.getLoc()))
+    return;
   mlir::ModuleOp module = getOperation();
   mlir::MLIRContext *context = &getContext();
   fir::DebugTypeGenerator typeGen(module);
@@ -163,12 +181,19 @@ void AddDebugInfoPass::handleGlobalOp(fir::GlobalOp globalOp,
   // declared. We are using a best guess of line - 1 where line is the source
   // line of the first member of the module that we encounter.
 
-  if (result.second.modules.empty())
-    return;
+  if (result.second.procs.empty()) {
+    // Only look for module if this variable is not part of a function.
+    if (result.second.modules.empty())
+      return;
 
-  scope = getOrCreateModuleAttr(result.second.modules[0], fileAttr, scope,
-                                line - 1, !globalOp.isInitialized());
+    // Modules are generated at compile unit scope
+    if (mlir::LLVM::DISubprogramAttr sp =
+            mlir::dyn_cast_if_present<mlir::LLVM::DISubprogramAttr>(scope))
+      scope = sp.getCompileUnit();
 
+    scope = getOrCreateModuleAttr(result.second.modules[0], fileAttr, scope,
+                                  line - 1, !globalOp.isInitialized());
+  }
   mlir::LLVM::DITypeAttr diType = typeGen.convertType(
       globalOp.getType(), fileAttr, scope, globalOp.getLoc());
   auto gvAttr = mlir::LLVM::DIGlobalVariableAttr::get(
@@ -182,6 +207,7 @@ void AddDebugInfoPass::handleGlobalOp(fir::GlobalOp globalOp,
 void AddDebugInfoPass::runOnOperation() {
   mlir::ModuleOp module = getOperation();
   mlir::MLIRContext *context = &getContext();
+  mlir::SymbolTable symbolTable(module);
   mlir::OpBuilder builder(context);
   llvm::StringRef fileName;
   std::string filePath;
@@ -218,17 +244,11 @@ void AddDebugInfoPass::runOnOperation() {
       llvm::dwarf::getLanguage("DW_LANG_Fortran95"), fileAttr, producer,
       isOptimized, debugLevel);
 
-  if (debugLevel == mlir::LLVM::DIEmissionKind::Full) {
-    // Process 'GlobalOp' only if full debug info is requested.
-    for (auto globalOp : module.getOps<fir::GlobalOp>())
-      handleGlobalOp(globalOp, fileAttr, cuAttr);
-  }
-
   module.walk([&](mlir::func::FuncOp funcOp) {
     mlir::Location l = funcOp->getLoc();
     // If fused location has already been created then nothing to do
     // Otherwise, create a fused location.
-    if (mlir::dyn_cast<mlir::FusedLoc>(l))
+    if (debugInfoIsAlreadySet(l))
       return;
 
     unsigned int CC = (funcOp.getName() == fir::NameUniquer::doProgramEntry())
@@ -293,9 +313,15 @@ void AddDebugInfoPass::runOnOperation() {
       return;
 
     funcOp.walk([&](fir::cg::XDeclareOp declOp) {
-      handleDeclareOp(declOp, fileAttr, spAttr, typeGen);
+      handleDeclareOp(declOp, fileAttr, spAttr, typeGen, &symbolTable);
     });
   });
+  // Process any global which was not processed through DeclareOp.
+  if (debugLevel == mlir::LLVM::DIEmissionKind::Full) {
+    // Process 'GlobalOp' only if full debug info is requested.
+    for (auto globalOp : module.getOps<fir::GlobalOp>())
+      handleGlobalOp(globalOp, fileAttr, cuAttr, &symbolTable);
+  }
 }
 
 std::unique_ptr<mlir::Pass>

flang/test/Integration/debug-fixed-array-type-2.f90

@@ -23,20 +23,17 @@ function fn1(a1, b1, c1) result (res)
 ! CHECK-DAG: ![[R1:.*]] = !DISubrange(count: 3, lowerBound: 1)
 ! CHECK-DAG: ![[SUB1:.*]] = !{![[R1]]}
 ! CHECK-DAG: ![[D1TY:.*]] = !DICompositeType(tag: DW_TAG_array_type, baseType: ![[INT]], elements: ![[SUB1]])
-! CHECK-DAG: !DILocalVariable(name: "d1"{{.*}}type: ![[D1TY]])
 
 ! CHECK-DAG: ![[R21:.*]] = !DISubrange(count: 2, lowerBound: 1)
 ! CHECK-DAG: ![[R22:.*]] = !DISubrange(count: 5, lowerBound: 1)
 ! CHECK-DAG: ![[SUB2:.*]] = !{![[R21]], ![[R22]]}
 ! CHECK-DAG: ![[D2TY:.*]] = !DICompositeType(tag: DW_TAG_array_type, baseType: ![[INT]], elements: ![[SUB2]])
-! CHECK-DAG: !DILocalVariable(name: "d2"{{.*}}type: ![[D2TY]])
 
 ! CHECK-DAG: ![[R31:.*]] = !DISubrange(count: 6, lowerBound: 1)
 ! CHECK-DAG: ![[R32:.*]] = !DISubrange(count: 8, lowerBound: 1)
 ! CHECK-DAG: ![[R33:.*]] = !DISubrange(count: 7, lowerBound: 1)
 ! CHECK-DAG: ![[SUB3:.*]] = !{![[R31]], ![[R32]], ![[R33]]}
 ! CHECK-DAG: ![[D3TY:.*]] = !DICompositeType(tag: DW_TAG_array_type, baseType: ![[REAL]], elements: ![[SUB3]])
-! CHECK-DAG: !DILocalVariable(name: "d3"{{.*}}type: ![[D3TY]])
 
 ! CHECK-DAG: !DILocalVariable(name: "a1", arg: 1{{.*}}type: ![[D1TY]])
 ! CHECK-DAG: !DILocalVariable(name: "b1", arg: 2{{.*}}type: ![[D2TY]])

flang/test/Transforms/debug-local-global-storage-1.fir

@@ -0,0 +1,52 @@
+// RUN: fir-opt --add-debug-info --mlir-print-debuginfo %s | FileCheck %s
+
+module attributes {dlti.dl_spec = #dlti.dl_spec<#dlti.dl_entry<i64, dense<64> : vector<2xi64>>, #dlti.dl_entry<!llvm.ptr<272>, dense<64> : vector<4xi64>>, #dlti.dl_entry<!llvm.ptr<271>, dense<32> : vector<4xi64>>, #dlti.dl_entry<!llvm.ptr<270>, dense<32> : vector<4xi64>>, #dlti.dl_entry<f128, dense<128> : vector<2xi64>>, #dlti.dl_entry<f80, dense<128> : vector<2xi64>>, #dlti.dl_entry<i128, dense<128> : vector<2xi64>>, #dlti.dl_entry<i8, dense<8> : vector<2xi64>>, #dlti.dl_entry<!llvm.ptr, dense<64> : vector<4xi64>>, #dlti.dl_entry<i1, dense<8> : vector<2xi64>>, #dlti.dl_entry<f16, dense<16> : vector<2xi64>>, #dlti.dl_entry<f64, dense<64> : vector<2xi64>>, #dlti.dl_entry<i32, dense<32> : vector<2xi64>>, #dlti.dl_entry<i16, dense<16> : vector<2xi64>>, #dlti.dl_entry<"dlti.stack_alignment", 128 : i64>, #dlti.dl_entry<"dlti.endianness", "little">>, fir.defaultkind = "a1c4d8i4l4r4", fir.kindmap = "", llvm.data_layout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"} {
+  func.func @_QMexamplePmod_sub() {
+    %c2 = arith.constant 2 : index
+    %1 = fir.address_of(@_QMexampleEmod_arr) : !fir.ref<!fir.array<2x2xi32>>
+    %2 = fircg.ext_declare %1(%c2, %c2) {uniq_name = "_QMexampleEmod_arr"} : (!fir.ref<!fir.array<2x2xi32>>, index, index) -> !fir.ref<!fir.array<2x2xi32>> loc(#loc4)
+    %3 = fir.address_of(@_QMexampleFmod_subEss) : !fir.ref<i32>
+    %4 = fircg.ext_declare %3 {uniq_name = "_QMexampleFmod_subEss"} : (!fir.ref<i32>) -> !fir.ref<i32> loc(#loc5)
+    return
+  } loc(#loc6)
+  func.func @_QQmain() attributes {fir.bindc_name = "test"} {
+    %c3 = arith.constant 3 : index
+    %c4 = arith.constant 4 : index
+    %1 = fir.address_of(@_QFEarr) : !fir.ref<!fir.array<3x4xi32>>
+    %2 = fircg.ext_declare %1(%c3, %c4) {uniq_name = "_QFEarr"} : (!fir.ref<!fir.array<3x4xi32>>, index, index) -> !fir.ref<!fir.array<3x4xi32>> loc(#loc2)
+    %3 = fir.address_of(@_QFEs) : !fir.ref<i32>
+    %4 = fircg.ext_declare %3 {uniq_name = "_QFEs"} : (!fir.ref<i32>) -> !fir.ref<i32> loc(#loc3)
+    return
+  } loc(#loc1)
+  fir.global @_QMexampleEmod_arr : !fir.array<2x2xi32> {
+    %0 = fir.zero_bits !fir.array<2x2xi32>
+    fir.has_value %0 : !fir.array<2x2xi32>
+  } loc(#loc4)
+  fir.global internal @_QMexampleFmod_subEss : i32 {
+    %c2_i32 = arith.constant 2 : i32
+    fir.has_value %c2_i32 : i32
+  } loc(#loc5)
+  fir.global internal @_QFEarr : !fir.array<3x4xi32> {
+    %0 = fir.zero_bits !fir.array<3x4xi32>
+    fir.has_value %0 : !fir.array<3x4xi32>
+  } loc(#loc2)
+  fir.global internal @_QFEs : i32 {
+    %c2_i32 = arith.constant 2 : i32
+    fir.has_value %c2_i32 : i32
+  } loc(#loc3)
+}
+#loc1 = loc("test.f90":21:1)
+#loc2 = loc("test.f90":22:1)
+#loc3 = loc("test.f90":23:1)
+#loc4 = loc("test.f90":5:1)
+#loc5 = loc("test.f90":12:1)
+#loc6 = loc("test.f90":10:1)
+
+// CHECK-DAG: #[[CU:.*]] = #llvm.di_compile_unit<{{.*}}>
+// CHECK-DAG: #[[MOD:.*]] = #llvm.di_module<{{.*}}scope = #[[CU]]{{.*}}name = "example"{{.*}}>
+// CHECK-DAG: #[[SP:.*]] = #llvm.di_subprogram<{{.*}}name = "_QQmain"{{.*}}>
+// CHECK-DAG: #[[MOD_SP:.*]] = #llvm.di_subprogram<{{.*}}name = "mod_sub"{{.*}}>
+// CHECK-DAG: #llvm.di_global_variable<scope = #[[SP]], name = "arr"{{.*}}line = 22{{.*}}>
+// CHECK-DAG: #llvm.di_global_variable<scope = #[[SP]], name = "s"{{.*}}line = 23{{.*}}>
+// CHECK-DAG: #llvm.di_global_variable<scope = #[[MOD_SP]], name = "ss"{{.*}}line = 12{{.*}}>
+// CHECK-DAG: #llvm.di_global_variable<scope = #[[MOD]], name = "mod_arr"{{.*}}line = 5{{.*}}>